If you're like most wireless LAN users, you probably don't give much thought to antennas; you just grin and bear it when signal strength and throughput degrade. But upgrading your antennas is an easy and cost-effective way to extend the reach of your WLAN.

When considering an antenna, first check to see whether your wireless CardBus adapter or AP allows you to attach one. If so, you must next decide which type of connector you need. APs typically use an SMA connector, and client cards use a variety of connectors, so you'll probably need a custom cable or adapter.

Next, you must decide which of the four types of antennas for 2.4 GHz to use, based on your needs.

Most WLAN APs ship with 4- or 6-dBi omnidirectional dipole antennas, which transmit in all directions around their axes. Clients located horizontally from the antennas receive the strongest signal, and clients located vertically (on another floor, for example) receive a weaker signal. Before adding an antenna, see whether repositioning your AP or client improves signal strength.

A directional antenna focuses signals in both the horizontal and vertical planes to produce hemispherical coverage approximately 30 degrees wide. It is typically of the flat-patch or panel variety, is mounted flat on walls or ceilings, and is good in areas where multiple clients access the WLAN from the same direction, like a conference room or a row of cubicles.

A Yagi antenna consists of a flat strip of metal with horizontal crossbars. It is high-gain and can be very directional, with a beam width as low as 15 degrees. It is also good for point-to-point communications, like connecting buildings on a campus.

A parabolic dish or grid antenna is a concave panel that usually produces an extremely high gain with a great degree of directionality (as precise as 4 degrees). Dishes can be solid or made of mesh (which is often suggested for high-wind situations). A dish provides the best bang for the buck, but some consider it unsightly. This type of antenna is good for long-range, point-to-point applications, like connecting two buildings that are more than a mile apart.

We put our hands on antennas of various prices and types for this story. For more on them, references on building your own antennas, and links to the best places to buy antennas online, click here.

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About the Author

Matthew D. Sarrel, CISSP, is managing director for CMG, a worldwide organization of IT performance and scalability professionals. He is also a technical marketing consultant and technical writer. To read his opinions on games please browse http://games.mattsarrel.com and for more general information on Matt, please see http://www.mattsarrel.com

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